Red Sox pick up another arm with stuff and potential

A deep-dive analysis on Zack Weiss, the newest Red Sox pitcher.

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The Red Sox picked up 6-foot-3 right-hander Zack Weiss Friday and assigned him to Triple-A Worcester. On paper, Weiss looks like your typical fringe reliever who’s up and down between the majors and Triple-A and could be DFA’d by next week. Which, in a sense he is. However, Weiss’ stuff could be developed into a very solid arm and is someone Boston might want to invest in.  

Weiss reminds me a bit of someone like Mauricio Llovera. Veteran two-pitch arm with solid stuff and an exact 5.1 innings of big-league experience via the time of the pickup. Like Llovera, control is a bit of an issue as well. Weiss’ 5.79 BB/9 is a heavy contributor to his 6.03 ERA in Triple-A this season. 

The righty’s arsenal however is favored by pretty much every model. FanGraphs and Pitch Profiler give both his fastball and slider/sweeper a 110–120 Stuff+ respectively, with PP additionally giving his arsenal a ~120 xWhiff+. And generally, Weiss sets a good number of guys down on strikes — he’s consistently put up an 11+ K/9 since 2021 in Triple-A. Also an 11.81 K/9 in the 5.1 big-league innings he’s had. 

The 31-year-old is a slider-first arm, throwing his slider roughly 2/3 of the time — it gets ~12" of sweep at a mid-7° VAA and 84 mph. It held a near 16 SwStr% in Triple-A with a 37% whiff rate and only an 85 avg EV while also getting an 18 SwStr% on 60 pitches with it in the majors. He seems to have tweaked it this offseason in making it more of a sweeper — he gave it roughly 2" less ride, 2 less mph, and an additional 2" of sweep. 

The fastball on the other hand gets a very nice 15–18" of ride and ~4" of run at 95 and a mid-4° VAA, but he only gets a low 80s% spin efficiency on the fastball — I’d like to see the Red Sox try and improve that number to give it more of a rising effect to help give it more life; which should generally help it out overall. It’s getting an ugly avg EV of 92 in Triple-A on top of the existing control issues — just a 22 CSW% compared to the slider’s 36%. 

He also throws a cutter; well, sort of. He’s hurled it just over 50 times in Triple-A this year compared to the several hundred fastballs and sliders. And when he got to the majors this year, he only threw it once — a pitch that almost hit Joey Gallo before he proceeded to homer on an inside fastball later in the at-bat. He threw it only nine times last year (6.6%) as well in the 13.1 innings he tossed for Los Angeles. It’s your average cutter; 88–90 mph at 1–3" of horizontal movement — why he’s not throwing it might just be as simple as a comfort level with the pitch. I don’t’ have Triple-A data from last year but during his big-league stint in ’22 he also tossed a sinker a few times, though he seems to have given that up. Developing a consistent third pitch for Weiss should be a priority.